/*
 * Copyright 2020 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkSLSampleUsage_DEFINED
#define SkSLSampleUsage_DEFINED

#include "include/core/SkTypes.h"

namespace SkSL {
/* *
 * Represents all of the ways that a fragment processor is sampled by its parent.
 */
class SampleUsage {
public:
    enum class Kind {
        // Child is never sampled
        kNone,
        // Child is only sampled at the same coordinates as the parent
        kPassThrough,
        // Child is sampled with a matrix whose value is uniform
        kUniformMatrix,
        // Child is sampled with sk_FragCoord.xy
        kFragCoord,
        // Child is sampled using explicit coordinates
        kExplicit,
    };

    // Make a SampleUsage that corresponds to no sampling of the child at all
    SampleUsage() = default;

    SampleUsage(Kind kind, bool hasPerspective) : fKind(kind), fHasPerspective(hasPerspective)
    {
        if (kind != Kind::kUniformMatrix) {
            SkASSERT(!fHasPerspective);
        }
    }

    // Child is sampled with a matrix whose value is uniform. The name is fixed.
    static SampleUsage UniformMatrix(bool hasPerspective)
    {
        return SampleUsage(Kind::kUniformMatrix, hasPerspective);
    }

    static SampleUsage Explicit()
    {
        return SampleUsage(Kind::kExplicit, false);
    }

    static SampleUsage PassThrough()
    {
        return SampleUsage(Kind::kPassThrough, false);
    }

    static SampleUsage FragCoord()
    {
        return SampleUsage(Kind::kFragCoord, false);
    }

    bool operator == (const SampleUsage &that) const
    {
        return fKind == that.fKind && fHasPerspective == that.fHasPerspective;
    }

    bool operator != (const SampleUsage &that) const
    {
        return !(*this == that);
    }

    // Arbitrary name used by all uniform sampling matrices
    static const char *MatrixUniformName()
    {
        return "matrix";
    }

    SampleUsage merge(const SampleUsage &other);

    Kind kind() const
    {
        return fKind;
    }

    bool hasPerspective() const
    {
        return fHasPerspective;
    }

    bool isSampled() const
    {
        return fKind != Kind::kNone;
    }
    bool isPassThrough() const
    {
        return fKind == Kind::kPassThrough;
    }
    bool isExplicit() const
    {
        return fKind == Kind::kExplicit;
    }
    bool isUniformMatrix() const
    {
        return fKind == Kind::kUniformMatrix;
    }
    bool isFragCoord() const
    {
        return fKind == Kind::kFragCoord;
    }

private:
    Kind fKind = Kind::kNone;
    bool fHasPerspective = false; // Only valid if fKind is kUniformMatrix
};
} // namespace SkSL

#endif
